Virtual Wind Tunnel analysis

Altair Forum User

Hi all,
 
New user to the whole suite so I may be a little slow at this.
 
We (members of Cardiff University) received training this week covering the majority of the HW suite. We touched on the VWT program and this is where my issue is. 
 
I'm trying to run an analysis with a small two element rear wing for a car. Tried following the tutorial (intersecting the model and the tunnel boundary) and I receive a meshing error (Can't perform mesh intersection between the body and the tunnel). So I tried moving the part into the middle of the tunnel, and although the part is detected in the final report (shows dimensions of part in table 2), it doesnt appear in any images and the flow doesnt seem to interact with it. 

 

I'm basically asking which one is correct and how I would solve the issues I'm having.
 
I can upload files as required etc. but for now I've just attached the report.

 

Thanks in advance,

John

 

Unable to find an attachment - read this blog

Altair Forum User

In the run directory you should find a *.nas file, which contains the wind tunnel and the body. Check if your wing is included.

 

Do you see similar behavior with a simple box which is intersecting the ground ?

ydigit

Are you using all tria elements in surface mesh? As per my experience a floating body with quad elements does not work and shows empty report like yours.

Could you upload .hm and/or .nas file?

 

Altair Forum User

Hi guys thanks for the replies,

I think from what Im reading of your replies is that the model has to been a surface model? Which may be where my issue is as it is all solid bodies. Can I mesh its as a surface in HM or will I have to remodel it?

 

And I tried to attach the .nas and .hm as requested but I got an error 500 with both so Ive linked to them underneath. Hopefully this doesnt break any forum rules.

 

Regards,

John

 

.NAS https://www.dropbox.com/s/wedydf1oo8iopj6/Meshed%20wing.nas

.HM https://www.dropbox.com/s/u7z9fu6uz0wzgi5/Meshed%20wing.hm

ydigit

You can mesh your solid model in HM using surface meshing, similar to

http://www.altairhyperworks.com/%28S%283fu2zyrlbyi03xcofiue25jd%29%29/hwhelp/Altair/hw11.0/help/hwtut/hwtut.htm?hypermesh_tutorials.htm

 

After creating surface mesh, make a few checks to ensure it is closed mesh: free edges, connectivity, duplicates, intersections as mentioned in

http://training.altairuniversity.com/analysis/cfd/efficient-cfd-meshing-workflow/

Altair Forum User

Hi ydigit, 

 

Im afraid your 1st link didnt work but I followed the second link. Unfortunately I got stuck where it said to 'clean up CAD geometry to generate water tight model e.g. edge edit, surface edit panels'. I don't have those buttons in my workspace and I'm afraid I don't know which menu to look for. Can you point me in the right direction?

 

And the next step to organise surfaces in components, do I just create 'dest' called walls for example?

 

John

ydigit

Seems first link is HW installation dependent. Sorry about that. 

 

I opened the HM file. There are several issue with this setup. There is only  a solid mesh and mesh between parts is not connected.

You would have to create a closed surface mesh. That means nodes between different components would have to be coincident.

One way to do that fast would be to boolean all solids and then create surface mesh.

 

You might want to get somebody with HM experience to help you out or maybe HM forum ?

Altair Forum User

Thanks ydigit,

 

I have made changes to that HM file due to the tutorial you posted so I have resolved so of the issues you mentioned but I will listen to your advice and move forums. 

 

Thanks,

John

Altair Forum User

When generating a surface mesh in HyperMesh for importing into VWT, it is recommended to use a tria mesh (e.g. generated with surface deviation) and export it as Nastran(Fluent). This export format will also add some dummy property cards into the exported *.nas mesh and ensures a proper import into VWT.